Technical Description - Marantz MM9000 Service Manual

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9. TECHNICAL DESCRIPTION

The Peak Detector (explanation about Front L CH)
1) First stage of QG01 <NJM4558DD> (on PG01) functions for comparator.
2) The input signal voltage at JE01 <INPUT Front L> (on PE01) is sent to the 3 pin of QG01 by way of CG01 (on PG01)
and RG01 (on PG01), part of Speaker Output voltage is sent to the 2 pin of QG01 by way of RN55 (on PT01), CG05
(on PG01) and RG06 (on PG01).
3) The 2 pin voltage is same to the 3 pin until about 1.5V input voltage at JE01. Therefor the 1 pin of QG01 output
voltage is 0V.
4) When input voltage at JE01 is more than 1.5V, Speaker Output voltage reaches at clipping level and the 2 pin
voltage is different from the 3 pin.
5) Then some voltage appears at the 1 pin of QG01.
6) Negative voltage is taken out by DG01 (on PG01) and DG02 (on PG01), then QG02 <2SA608SP/ETC> (on PG01)
becomes ON and PEAK LED turns on.
Notice: The PEAK LED turns on little in usual operation, This turns on when input voltage at JE01 becomes 1.5V over
and Speaker Output voltage is more than 36V.
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